Prevention of disease in ferrets fed an inactivated whole cell Campylobacter jejuni vaccine

Ferrets were used to demonstrate the potential of a killed whole cell vaccine prepared from Campylobacter jejuni to protect against disease. C. jejuni strain 81-176 was grown in BHI broth, formalin-fixed, and resuspended in PBS to a concentration of 10¹⁰ cells per ml. This vaccine (CWC) or live organisms were delivered orally with a nasogastric tube into anesthetized animals treated to reduce gastric acidity and intestinal motility. When 5 × 10¹⁰ CFU of the vaccine strain (Lior serotype 5) or one of two other serotypes, CGL-7 (Lior 4) or BT44 (Lior 9), was used to challenge the ferrets, all of the animals developed a mucoid diarrhea. If the animals had been challenged with 5 × 10⁹ CFU of the homologous strain 1 month before challenge with 10¹⁰ CFU, 80-100% protection against disease was seen. This protection was also obtained after an initial exposure to the 81-176 strain followed by challenge with either of the heterologous strains. CWC was used to see if protection demonstrated with the live organisms could be produced with the non-living preparation. When 10⁹ cells of CWC was given as two doses 7 days apart with or without 25 μg of a coadministered mucosal adjuvant, LT_R192G, only 40-60% of the animals were protected. If the regimen was changed to four doses given 48 h apart, 80% of the animals were free of diarrhea after subsequent challenge. Increasing the number of cells in the four dose regimen to 10¹⁰ cells did not improve protection. Animals given four doses of 10¹⁰ cells combined with LT _R192G were subsequently challenged with 10¹⁰ cells of the homologous strain or the heterologous strain CGL-7. The CWC protected against both strains. Serum IgG antibody titers determined by ELISA showed little increase following the CWC four dose vaccination regimen, compared to animals given one dose of the live organism. On subsequent challenge, however, both CWC vaccinated and live-challenged ferrets showed comparable antibody titer increases above those obtained following the initial challenge or vaccination. Western blots were used to show that the immunodominant antigen in vaccinated animals was a 45 kDa protein, while in ferrets challenged with live organisms the immunodominant antigen was a 62 kDa protein. These data show that the CWC can be used to protect against disease caused by Campylobacter. They also show that protection and serum IgG responses do not depend upon the use of the mucosal adjuvant and that cross protection among some of the major serotypes of Campylobacter responsible for human disease is possible.